Colin Gray, the father of the teenager accused of killing four people at a Georgia high school, knew of his son’s deteriorating mental state and his fascination with campus shootings, investigators testified Wednesday during a hearing that elicited troubling new details of what led up to the rampage.

Private notebooks reveal the alleged Georgia school shooter made meticulous plans to kill students and teachers ahead of the deadly tragedy at Apalachee High School. "Shoot the teacher first," Colt Gray wrote in a notebook found by investigators in his bedroom,